# US 11,309,487 B2 · Spin transfer torque MRAM with a spin torque oscillator stack and methods of making the same

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- Number: US 11,309,487 B2
- Document ID: US11309487B2
- Status: Granted
- Kind: B2
- Application number: 16/880,497
- Filed: 2020-05-21
- Published: 2020-09-10
- Granted: 2022-04-19
- Earliest claimed: 2018-12-06
- Assignees: SanDisk Technologies LLC
- Applicants: Sandisk Technologies LLC
- Inventors: Quang Le; Zhanjie Li; Zhigang Bai; Paul Vanderheijden; Michael Ho
- Web page: https://patentgrep.com/patent/US11309487B2

## CPC

- H10N 50/80: Constructional details
- G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell}
- H01F 10/3254: {the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]}
- H01F 10/3268: {the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn}
- H01F 10/329: {Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect}
- H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10N 50/10: Magnetoresistive devices
- H10N 50/85: Materials of the active region
- G11C 11/1655: {Bit-line or column circuits}
- G11C 11/1657: {Word-line or row circuits}
- G11C 11/1673: {Reading or sensing circuits or methods}
- H01F 10/3272: {by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets}
- H01F 10/3286: {Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy}
- H10N 50/01: Manufacture or treatment
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- G11C: STATIC STORES (semiconductor memory devices H10B)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H10B: ELECTRONIC MEMORY DEVICES

## Abstract

A MRAM cell includes a magnetic tunnel junction containing a reference layer having a fixed magnetization direction, a free layer, and a nonmagnetic tunnel barrier layer located between the reference layer and the free layer, a spin torque oscillator stack, and a first nonmagnetic spacer layer located between the free layer and the spin torque oscillator stack.

## Claims

### Claim 1

A MRAM cell, comprising:
a magnetic tunnel junction comprising a reference layer having a fixed magnetization direction, a free layer, and a nonmagnetic tunnel barrier layer located between the reference layer and the free layer;
a spin torque oscillator stack; and
a first nonmagnetic spacer layer located between the free layer and the spin torque oscillator stack,
wherein:
the spin torque oscillator stack comprises a spin torque layer, a spin polarization layer and a second nonmagnetic spacer located between the spin torque layer and the spin polarization layer;
the spin torque layer comprises a first magnetic material having a first conical magnetization with respect to a vertical axis that is parallel to the fixed vertical magnetization direction of the reference layer; and
an in-plane component of the first conical magnetization is free to precess around the vertical axis upon application of current through the spin torque layer, the second nonmagnetic spacer layer, and the spin polarization layer.

### Claim 2 (depends on 1)

The MRAM cell of claim 1, wherein the spin torque layer is located on the first nonmagnetic spacer layer, the second nonmagnetic spacer layer is located on the spin torque layer, and the spin polarization layer is located on the second nonmagnetic spacer layer.

### Claim 3 (depends on 1)

The MRAM cell of claim 1, further comprising a nonmagnetic capping layer located over the spin polarization layer and comprising a metallic material.

### Claim 4 (depends on 1)

The MRAM cell of claim 1, wherein the spin torque oscillator stack is configured to provide an initial non-vertical torque to a magnetization of the free layer during an initial phase of precession of the magnetization of the free layer around a vertical axis that is parallel to the fixed vertical magnetization direction of the reference layer upon initiation of flow of current through the MRAM cell.

### Claim 5 (depends on 1)

The MRAM cell of claim 1, wherein the spin torque layer is more proximal to the first nonmagnetic spacer layer than the spin polarization layer is to the first nonmagnetic spacer layer.

### Claim 6 (depends on 1)

The MRAM cell of claim 1, wherein the spin torque layer is in direct contact with the first nonmagnetic spacer layer.

### Claim 7 (depends on 1)

The MRAM cell of claim 1, wherein the spin polarization layer comprises a second magnetic material having a second conical magnetization with respect to the vertical axis that is parallel to the fixed vertical magnetization direction of the reference layer.

### Claim 8 (depends on 7)

The MRAM cell of claim 7, wherein an in-plane component of the second conical magnetization is free to precess around the vertical axis upon application of current through the spin torque layer, the second nonmagnetic spacer layer, and the spin polarization layer.

### Claim 9 (depends on 7)

The MRAM cell of claim 7, wherein the fixed vertical magnetization direction of the reference layer maintains a same orientation upon application of electrical current through the reference layer.

### Claim 10 (depends on 7)

The MRAM cell of claim 7, wherein the spin polarization layer comprises a ferromagnetic material having the second conical magnetization with respect to the vertical axis.

### Claim 11 (depends on 10)

The MRAM cell of claim 10, wherein the ferromagnetic material has an axial magnetization component that is parallel or antiparallel to an axial magnetization component of the first conical magnetization of the spin torque layer.

### Claim 12 (depends on 1)

The MRAM cell of claim 1, wherein the spin polarization layer comprises:
a first spin polarization component layer having zero or negative magnetization; and
a second spin polarization component layer having an axial magnetization that is parallel or antiparallel to the vertical axis.

### Claim 13 (depends on 12)

The MRAM cell of claim 12, wherein the second spin polarization component is vertically spaced from the first spin polarization component layer by a third nonmagnetic spacer layer.

### Claim 14 (depends on 12)

The MRAM cell of claim 12, wherein the second spin polarization component comprises a multilayer stack of cobalt layers and at least one of platinum or palladium layers.

### Claim 15 (depends on 14)

The MRAM cell of claim 14, wherein the first spin polarization component comprises a cobalt-iridium alloy comprising 70 to 90 atomic percent cobalt and 10 to 30 atomic percent iridium.

### Claim 16 (depends on 14)

The MRAM device of claim 14, wherein the first spin polarization component comprises a cobalt-iron alloy comprising 90 to 99.5 atomic percent cobalt and 0.5 to 10 atomic percent iron.

### Claim 17 (depends on 14)

The MRAM device of claim 14, wherein the first spin polarization component comprises a cobalt-iron-boron alloy.

### Claim 18 (depends on 14)

The MRAM device of claim 14, wherein the first spin polarization component comprises a multilayer stack of cobalt layers and iron layers.

### Claim 19 (depends on 14)

The MRAM device of claim 14, wherein a combined magnetization of the first spin polarization component layer and the second spin polarization component layer provides the second conical magnetization that is coupled to the first conical magnetization of the spin torque layer.

### Claim 20 (depends on 1)

A method of operating the MRAM device of claim 1, comprising programming the MRAM device by flowing the current through the magnetic tunnel junction, the spin torque oscillator stack and the first nonmagnetic spacer layer,
wherein the in-plane component of the first conical magnetization is free to precess around the vertical axis when the current flows through the magnetic tunnel junction, the spin torque oscillator stack and the first nonmagnetic spacer layer.